EP1002806B1 - Verfahren zur Herstellung eines hydrophilen Polymer - Google Patents

Verfahren zur Herstellung eines hydrophilen Polymer Download PDF

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EP1002806B1
EP1002806B1 EP99122561A EP99122561A EP1002806B1 EP 1002806 B1 EP1002806 B1 EP 1002806B1 EP 99122561 A EP99122561 A EP 99122561A EP 99122561 A EP99122561 A EP 99122561A EP 1002806 B1 EP1002806 B1 EP 1002806B1
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weight
hydrogel polymer
water
water content
polymer
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EP1002806A1 (de
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Yorimichi Dairoku
Koji Miyake
Yasuhiro Fujita
Yoshio Irie
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Nippon Shokubai Co Ltd
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Nippon Shokubai Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments
    • C08F6/02—Neutralisation of the polymerisation mass, e.g. killing the catalyst also removal of catalyst residues
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments
    • C08F6/001—Removal of residual monomers by physical means
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments
    • C08F6/008—Treatment of solid polymer wetted by water or organic solvents, e.g. coagulum, filter cakes

Definitions

  • the present invention relates to a production process for a hydrophilic polymer such as a water-soluble or water-swellable polymer, and, in more detail, to a process for producing a hydrophilic polymer having a low residual monomer content while retaining the properties of a hydrogel polymer resultant from polymerization.
  • a hydrophilic polymer such as a water-soluble or water-swellable polymer
  • Hydrophilic polymers are represented by water-soluble polymers and water-swellable polymers.
  • the water-soluble polymer include: sodium polyacrylate; partially hydrolyzed products of polyacrylamide; and polyvinyl alcohol. These water-soluble polymers are, for example, used for: flocculants for water treatment; mud additives for petroleum excavation; and food additives.
  • the water-swellable polymer include: crosslinked polyacrylate salts; saponified products of acrylic acid ester-vinyl acetate copolymers; modified products of crosslinked polyvinyl alcohol; crosslinked products of partially neutralized polyacrylate salts; crosslinked products of isobutylene-maleic anhydride copolymers; and starch-acrylic acid grafted polymers.
  • EP-A-0,412,363 discloses treating a water-containing finely-divided polymer gel with steam such that solids content of the gel is increased by no more than 30 wt.%. The polymer gel is then conventionally dried.
  • processes to reduce the residual monomer content in the polymer generally, for example, there are the following proposed processes: a process in which ammonia or an amine (JP-B-33-002646 and JP-A-50-040689) or a sulfite or hydrogensulfite salt (USP 2,960,486 and JP-A-55-135110) is added to cause addition reactions of these compounds to the residual monomer, thereby reducing the residual monomer content; and a process in which a low or high temperature decomposition type polymerization initiator (JP-B-50-044280, JP-A-59-133205, and JP-A-53-141388) or a combination of a redox catalyst and an azo initiator (JP-A-50-096689 and JP-B-47-026430) is further used to polymerize the residual monomer, thereby reducing the residual monomer content.
  • a low or high temperature decomposition type polymerization initiator JP-B-50-044280, J
  • ammonia, the amine, or the sulfite or hydrogensulfite salt may be effective in the reduction of the residual monomer content, but, in the case where the amount of these compounds as added is small, there is no effect, and further, there are problems of toxicity of these additives themselves.
  • the process, involving the further use of the catalyst merely has insufficient effects.
  • the microwave irradiation in the drying step involves local heating of materials to change the properties of the hydrogel polymer, and further, has many problems to overcome in the future in respect to the safety of the microwave itself, the restriction of materials in the vicinity of the microwave irradiation, and high cost of devices, therefore, is not practical in the current state.
  • an object of the present invention is to provide a production process to obtain a hydrophilic polymer, having a low residual monomer content, with good productivity while keeping the properties of a hydrogel polymer resultant from polymerization.
  • the hydrogel polymer to be dried in the present invention is a water-soluble or water-swellable hydrogel as obtained by aqueous solution polymerization of a hydrophilic monomer, and contains the unreacted residue of the monomer. If necessary, this hydrogel polymer may be a particulate hydrogel polymer as divided into small pieces to ensure a surface area needed for drying.
  • hydrogel polymer examples include:
  • hydrophilic monomer examples include: (meth)acrylic acid, or alkaline metal or ammonium salts thereof; (meth)acrylamide; (meth)acrylonitrile; unsaturated dibasic acids such as maleic acid and fumaric acid, or half esters of these unsaturated dibasic acids, or alkaline metal or ammonium salts of these dibasic acids or half esters; unsaturated sulfonic acids such as 2-acrylamido-2-methylpropanesulfonic acid and 2-(meth)acryloylethanesulfonic acid, or alkaline metal or ammonium salts thereof; and 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.
  • hydrophilic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, vinyl acetate, and vinyl propionate, may be used in such an amount as not to extremely damage the hydrophilicity of the resultant hydrogel polymer.
  • a crosslinking agent may be jointly used with the above hydrophilic monomer.
  • crosslinking agent examples include ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, N,N-methylenebisacrylamide, triallyl isocyanurate, pentaerythritol diacrylate, and pentaerythritol dimethacrylate.
  • the polymerization for obtaining the hydrogel polymer is the aqueous solution polymerization of the hydrophilic monomer, and is generally achieved by dissolving a hydrophilic monomer component, a polymerization initiator, and a crosslinking agent (as used if necessary) into water, and then degassing the resultant aqueous hydrophilic monomer solution with an inert gas such as nitrogen gas, and then carrying out a polymerization process of which examples include: as is disclosed in JP-B-48-042466, a casting polymerization process in which the aqueous monomer solution is placed into a formwork to polymerize the solution; as is disclosed in JP-A-58-049714, a process in which the polymerization is carried out on a belt conveyer; and, as is disclosed in JP-A-57-034101, a process in which the polymerization is carried out in a device such as a kneader that contains agitation vanes which can divide the resultant hydrogel poly
  • the polymerization initiator is usable without especial limitation, and examples thereof include ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, and 2,2'-azobis(2-amidinopropane) dihydrochloride.
  • redox initiators which are combinations of the above initiators with reducing agents such as sodium hydrogensulfite, L-ascorbic acid, and ferrous salts, are also usable.
  • the persulfate salts have so high pyrolysis temperature as to easily remain even in the hydrogel polymer resultant from the polymerization, therefore, if they are reacted with residual monomers, the residual monomer content can be reduced.
  • the water content of the hydrogel polymer is preferably in the range of 80 ⁇ 60 weight %.
  • the water content of the hydrogel polymer can be adjusted with the concentration of the aqueous hydrophilic monomer solution.
  • the amount of the polymerization initiator, as used relative to the monomer, is in the range of usually 0.0001 ⁇ 3 weight %, preferably 0.0002 ⁇ 2 weight %, for the water-soluble polymer, and in the range of usually 0.01 ⁇ 2 weight %, preferably 0.05 ⁇ 1 weight %, for the water-swellable polymer.
  • the hydrogel polymer as obtained by polymerization might be an already disintegrated one, but, in many cases, the hydrogel polymer needs to be small divided so as to be easy to dry.
  • effective methods for the small division include disintegration with a device such as a meat chopper, an extruder, or a kneader.
  • the residual monomer content of the hydrogel polymer is usually not lower than 1,000 ppm, but the drying process according to the present invention involves the use of a hydrogel polymer having a residual monomer content of usually not lower than 10,000 ppm, preferably not lower than 20,000 ppm, more preferably not lower than 30,000 ppm, most preferably not lower than 40,000 ppm.
  • An attempt to reduce the residual monomer content only by polymerization would result in so long a polymerization time as to deteriorate the productivity.
  • an attempt to reduce the residual monomer content using a large amount of polymerization initiator would result in the deterioration of the properties, such as decrease of the absorption capacity under no load or increase of the extractable content, of the resultant water-absorbent resin.
  • the present invention is achieved by a drying process for a hydrogel polymer which comprises the steps of: drying the hydrogel polymer under normal pressure at a material temperature of not higher than 90 °C until the water content of the hydrogel polymer reduces to 15 ⁇ 40 weight % (partial drying step); and then heat-aging the hydrogel polymer by keeping the hydrogel polymer for not shorter than 10 minutes either in a state where the change of the water content of the hydrogel polymer is within 5 weight % and where the material temperature is in the range of 70 ⁇ 120 °C or in a state where the water content of the hydrogel polymer is in the range of 15 ⁇ 40 weight % and where the material temperature is in the range of 70 ⁇ 120°C (heat-aging step); and then finish-drying the hydrogel polymer until the water content of the hydrogel polymer reduces to a desired value (finish-drying step).
  • the partial drying step is carried out under normal pressure, when the material temperature is not higher than 90 °C, preferably not higher than 80 °C.
  • the case where the material temperature is higher than 90 °C has the disadvantage of increasing the residual monomer content or deteriorating the hydrogel.
  • the drying under vacuum involves the device cost up of the drying oven and needs a long drying time, therefore, is not practical.
  • the partial drying step is carried out until the water content of the hydrogel polymer reduces to 15 ⁇ 40 weight %, preferably to 20 ⁇ 35 weight %.
  • the effect to reduce the residual monomer content in the subsequent heat-aging step is insufficient, and further, the hydrogel polymer is greatly deteriorated and the extractable content increases.
  • the effect to reduce the residual monomer content is poor.
  • the heat-aging step which is to keep the hydrogel polymer for not shorter than 10 minutes either in a state where the change of the water content of the hydrogel polymer is within 5 weight % and where the material temperature is in the range of 70 ⁇ 120 °C or in a state where the water content of the hydrogel polymer is in the range of 15 ⁇ 40 weight % and where the material temperature is in the range of 70 ⁇ 120 °C, can be realized, for example, by heating the hydrogel polymer in an airtight vessel to suppress the drying, or by lessening the wind amount in the case of hot-air drying, or by filling the drying oven with water vapor.
  • the material temperature is in the range of 70 ⁇ 120 °C, preferably 80 ⁇ 100 °C.
  • the material temperature exceeds 120 °C would result in the great deterioration of the polymer and in the increase of the water-soluble polymer content.
  • the aging period of time is not shorter than 10 minutes, preferably not shorter than 20 minutes. In the case where the aging period of time is shorter than 10 minutes, the effect to reduce the residual monomer content is insufficient.
  • the water content is kept in the range of 15 ⁇ 40 weight %, preferably 20 ⁇ 35 weight %, or the change of the water content is kept within 5 weight %, preferably within 4 weight %.
  • the material which has been subjected to the heat-aging step can be finish-dried until the water content is in a range of 0 ⁇ 10 weight %, when the drying temperature is preferably in the range of 80 ⁇ 250 °C, more preferably 80 ⁇ 170 °C for preventing the deterioration of the hydrogel polymer.
  • the drying temperature is either the temperature of the gas, as used, or the temperature of the material to be dried.
  • the water content in the range of 0 ⁇ 10 weight %, preferably 3 ⁇ 7 weight %. 99247
  • the form of the drying oven is not especially limited, but examples thereof include conductive heat-transfer drying ovens, radiative heat-transfer drying ovens, and hot-air heat-transfer drying ovens.
  • the hot-air heat-transfer drying oven (hereinafter referred to as "hot-air drying oven") is particularly preferable for the steps as particularly aimed at drying, such as the partial drying step, the finish-drying step, and later steps.
  • the hot-air drying oven include devices of the following types: through-flow band type, through-flow rotary type, through-flow tower type, parallel-flow band type, through-flow tunnel type, through-flow channel stirring type, fluidized-bed type, gas current type, and spray type.
  • Examples of the radiative heat-transfer type device include infrared and far-infrared drying ovens.
  • examples of the conductive heat-transfer type device include paddle dryers and drum dryers.
  • the gas as used for drying is not especially limited, but examples thereof include air, nitrogen, carbon dioxide, helium, and water vapor.
  • the hydrogel polymer is dried to obtain the aimed hydrophilic polymer. After being dried, the hydrogel polymer is pulverized, and then classified (if necessary), and then, preferably in the case of the water-swellable polymer, subjected to a surface-crosslinking treatment by a conventional method.
  • the surface-crosslinking treatment is, for example, carried out as follows: particles of the water-swellable polymer are mixed with a surface-crosslinking agent which is reactable with functional groups (e.g. acidic groups) of surfaces of the water-swellable polymer particles; and then, if necessary according to the type of the surface-crosslinking agent, the resultant mixture is heated; thus crosslinking the surface neighborhood.
  • the amount of the surface-crosslinking agent, as used, is preferably in the range of 0.01 ⁇ 10 weight parts, more preferably 0.5 ⁇ 5 weight parts, per 100 weight parts of the water-swellable polymer.
  • the surface-crosslinking agent examples include: polyhydric alcohol compounds such as ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol and sorbitol; polyepoxy compounds such as ethylene glycol diglycidy
  • the process according to the present invention can produce a hydrophilic polymer, having a low residual monomer content, with good productivity while keeping the properties of a hydrogel polymer resultant from polymerization, that is to say, preventing the polymer from being deteriorated due to drying.
  • the drying step can keep the absorption capacity change ratio not higher than 10 under no load and the extractable content change ratio not higher than 100, and further, can reduce the residual monomer content to not higher than 300 ppm.
  • the hydrophilic polymer as produced by the process according to the present invention, has little bad influence upon human bodies or environment, and is favorably used, for example, for the following purposes: flocculants for water treatment; mud additives for petroleum excavation; food additives; absorbing agents for sanitary materials; water-holding agents; and food-freshness-retaining films.
  • the water content, the solid content, the absorption capacity under no load, the extractable content, the residual monomer content, the absorption capacity under a load, and the swollen-gel pressure were measured by the following methods.
  • W1 (g) (about 0.2 g as 100 % solid content) of either a particulate hydrogel polymer, as converted into small particles of not greater than 1 mm, or a powder, as classified into 300 ⁇ 500 ⁇ m by pulverization, (both of which had a solid content of A (weight %)) was placed into a nonwoven-fabric-made bag (60 mm ⁇ 60 mm) and then immersed into a 0.9 weight % aqueous sodium chloride solution. Sixteen hours later, the bag was drawn up and then drained at 250 G for 3 minutes with a centrifuge, and the resultant weight W2 (g) of the bag was then measured.
  • W3 (g) (about 0.5 g as 100 % solid content) of either a particulate hydrogel polymer, as converted into small particles of not greater than 1 mm, or a powder, as classified into 300 ⁇ 500 ⁇ m by pulverization, (both of which had a solid content of A (weight %)) was dispersed into 1,000 g of deionized water, and then stirred for 16 hours.
  • the resultant mixture was filtered with filter paper, and 50 g of the resultant filtrate was placed into a beaker of 100 ml.
  • Extractable content (weight %) (C - B) ⁇ 0.005 ⁇ D/W3 ⁇ (100/A)
  • Extractable content change ratio (%)
  • the surface-crosslinked water-absorbent resin was allowed to absorb artificial urine under a load of 0.7 psi for 1 hour, and the resultant amount of the absorption was divided by the weight of the water-absorbent resin to determine the absorption capacity under the load, wherein the artificial urine was an aqueous solution containing sodium sulfate of 0.2 weight %, potassium chloride of 0.2 weight %, magnesium chloride hexahydrate of 0.05 weight %, calcium chloride dihydrate of 0.025 weight %, ammonium dihydrogenphosphate of 0.035 weight %, and diammonium hydrogenphosphate of 0.015 weight % in concentration respectively.
  • the measurement was made with a measurement device having a structure of Fig. 1 (Accuforce Cadet Force Gage (digital force gage), made by The Crown Tool and Supply Company) in the following way.
  • An amount of 0.358 g of water-absorbent resin a as classified into 300 ⁇ 600 ⁇ m, was placed into a cell b for FISHER ELECTRO-PHOTOMETER, and 10 g of artificial urine c having an adjusted temperature of 25 °C was also placed into the above cell b .
  • a polyethylene-made lid d was floated in the cell, and a disk e was piled up on the lid d .
  • aqueous monomer solution comprising 204 g of acrylic acid, 496 g of sodium acrylate, 1.6 g of polyethylene glycol diacrylate, and 1,286 g of water, was placed into a stainless vat of 220 mm ⁇ 300 mm, and then air in the reaction system was displaced with nitrogen while the temperature of the solution was kept at 20 °C.
  • the stainless vat was cooled for 20 minutes by immersion into a water bath of 20 °C, and then aging was made with warm water of 60 °C for 10 minutes.
  • the resultant polymer gel was divided with a meat chopper (made by Hiraga Seisakusho Co., Ltd.), thus obtaining a particulate hydrogel of about 3 mm in average particle diameter and of 65 weight % in water content.
  • aqueous monomer solution comprising 204 g of acrylic acid, 496 g of sodium acrylate, 1.6 g of polyethylene glycol diacrylate, and 1,286 g of water, was placed into a stainless vat of 220 mm ⁇ 300 mm, and then air in the reaction system was displaced with nitrogen while the temperature of the solution was kept at 20 °C.
  • aqueous monomer solution was stirred with a magnetic stirrer, thereto 3 g of 5 weight % aqueous V-50 solution, 3 g of 5 weight % aqueous sodium persulfate solution, 3 g of 0.5 weight % aqueous sodium L-ascorbate solution, and 3.5 g of 0.35 weight % aqueous hydrogen peroxide solution were added as polymerization initiators. About 1 minute later than the addition of the polymerization initiators, a polymerization reaction started. The stainless vat was cooled for 20 minutes by immersion into a water bath of 20 °C, and then aging was made with warm water of 60 °C for 40 minutes. The resultant polymer gel was divided with a meat chopper (made by Hiraga Seisakusho Co., Ltd.), thus obtaining a particulate hydrogel of about 3 mm in average particle diameter and of 65 weight % in water content.
  • a meat chopper made by Hiraga Seisakusho Co., Ltd.
  • aqueous monomer solution comprising 204 g of acrylic acid, 496 g of sodium acrylate, 1.6 g of polyethylene glycol diacrylate, and 1,286 g of water, was placed into a stainless vat of 220 mm ⁇ 300 mm, and then air in the reaction system was displaced with nitrogen while the temperature of the solution was kept at 20 °C.
  • aqueous monomer solution was stirred with a magnetic stirrer, thereto 3 g of 5 weight % aqueous V-50 solution, 6 g of 5 weight % aqueous sodium persulfate solution, 3 g of 0.5 weight % aqueous sodium L-ascorbate solution, and 3.5 g of 0.35 weight % aqueous hydrogen peroxide solution were added as polymerization initiators. About 1 minute later than the addition of the polymerization initiators, a polymerization reaction started. The stainless vat was cooled for 20 minutes by immersion into a water bath of 20 °C, and then aging was made with warm water of 60 °C for 30 minutes. The resultant polymer gel was divided with a meat chopper (made by Hiraga Seisakusho Co., Ltd.), thus obtaining a particulate hydrogel of about 3 mm in average particle diameter and of 65 weight % in water content.
  • a meat chopper made by Hiraga Seisakusho Co., Ltd.
  • aqueous monomer solution comprising 204 g of acrylic acid, 496 g of sodium acrylate, 1.6 g of polyethylene glycol diacrylate, and 1,286 g of water, was placed into a stainless vat of 220 mm ⁇ 300 mm, and then air in the reaction system was displaced with nitrogen while the temperature of the solution was kept at 20 °C.
  • aqueous monomer solution was stirred with a magnetic stirrer, thereto 3 g of 5 weight % aqueous V-50 solution, 9 g of 5 weight % aqueous sodium persulfate solution, 3 g of 0.5 weight % aqueous sodium L-ascorbate solution, and 3.5 g of 0.35 weight % aqueous hydrogen peroxide solution were added as polymerization initiators. About 1 minute later than the addition of the polymerization initiators, a polymerization reaction started. The stainless vat was cooled for 20 minutes by immersion into a water bath of 20 °C, and then aging was made with warm water of 60 °C for 30 minutes. The resultant polymer gel was divided with a meat chopper (made by Hiraga Seisakusho Co., Ltd.), thus obtaining a particulate hydrogel of about 3 mm in average particle diameter and of 65 weight % in water content.
  • a meat chopper made by Hiraga Seisakusho Co., Ltd.
  • a cap was attached to a jacketed stainless twin-arm type kneader of 10 liters in capacity and of 240 mm in depth having an opening portion of 220 mm ⁇ 260 mm and two sigmoidal vanes of 120 mm in rotational diameter. Then, an aqueous monomer solution, comprising 408 g of acrylic acid, 992 g of sodium acrylate, 3.2 g of polyethylene glycol diacrylate, and 2,572 g of water, was placed into the kneader, and then air in the reaction system was displaced with nitrogen while the liquid temperature of the aqueous monomer solution was kept at 25 °C by circulating warm water of 25 °C through the jacket.
  • aqueous monomer solution was stirred at 40 rpm with the two sigmoidal vanes, thereto 6 g of 5 weight % aqueous V-50 solution, 6 g of 5 weight % aqueous sodium persulfate solution, 6 g of 0.5 weight % aqueous sodium L-ascorbate solution, and 7 g of 0.35 weight % aqueous hydrogen peroxide solution were added as polymerization initiators. After the addition of the polymerization initiators, a polymerization reaction started in about 1 minute, and the temperature in the reaction system reached its peak in 15 minutes, when the temperature was 63 °C.
  • the temperature of the warm water in the jacket was raised to 60 °C to carry out aging for 10 minutes.
  • the resultant polymer gel was divided with a meat chopper (made by Hiraga Seisakusho Co., Ltd.), thus obtaining a particulate hydrogel of about 3 mm in average particle diameter and of 65 weight % in water content.
  • a particulate hydrogel was obtained in the same way as of Production Example 1 except that the amount of polyethylene glycol diacrylate, as used, was changed to 0.8 g.
  • aqueous monomer solution comprising 184 g of acrylic acid, 1,611 g of 37 weight % aqueous sodium acrylate solution, 4.3 g of polyethylene glycol diacrylate, and 194 g of water, was placed into a stainless vat of 220 mm ⁇ 300 mm, and then air in the reaction system was displaced with nitrogen while the temperature of the solution was kept at 18 °C. Next, while the aqueous monomer solution was stirred with a magnetic stirrer, thereto 5.3 g of 20 weight % aqueous sodium persulfate solution and 1.6 g of 5 weight % aqueous sodium L-ascorbate solution were added as polymerization initiators.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 20 minutes at a wind speed of 1 m/sec and a temperature of 80 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.) (partial drying step).
  • a thermometer was stuck into the central portion of the resultant lumpish aggregate to measure the material temperature, which was 70 °C.
  • the water content was 25 weight %.
  • the resultant aggregated semidry product was placed into a stainless beaker, and this vessel was airtightened by wrapping the entirety thereof with aluminum foil, and then heated at 100 °C for 1 hour (heat-aging step).
  • the semidry product After being heated, the semidry product had a material temperature of 95 °C and a water content of 23 weight %. Thereafter, the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven (finish-drying step), thus obtaining a dried product having a water content of 7 weight %. This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • the material temperature and the water content were 70 °C and 25 weight % respectively after the partial drying step; and the material temperature and the water content were 95 °C and 23 weight % respectively after the heat-aging step; and the water content was 7 weight % after the finish-drying step.
  • the material temperature and the water content were 73 °C and 24 weight % respectively after the partial drying step; and the material temperature and the water content were 96 °C and 22 weight % respectively after the heat-aging step; and the water content was 6 weight % after the finish-drying step.
  • the material temperature and the water content were 72 °C and 25 weight % respectively after the partial drying step; and the material temperature and the water content were 96 °C and 24 weight % respectively after the heat-aging step; and the water content was 7 weight % after the finish-drying step.
  • the material temperature and the water content were 72 °C and 25 weight % respectively after the partial drying step; and the material temperature and the water content were 95 °C and 25 weight % respectively after the heat-aging step; and the water content was 6 weight % after the finish-drying step.
  • the material temperature and the water content were 71 °C and 24 weight % respectively after the partial drying step; and the material temperature and the water content were 96 °C and 23 weight % respectively after the heat-aging step; and the water content was 7 weight % after the finish-drying step.
  • the material temperature and the water content were 70 °C and 25 weight % respectively after the partial drying step; and the material temperature and the water content were 97 °C and 24 weight % respectively after the heat-aging step; and the water content was 7 weight % after the finish-drying step.
  • the aggregated semidry product, resultant from the partial drying step in Example 1, was placed into a stainless autoclave, which was then airtightened and then heated at 120 °C for 12 minutes. After being heated, the semidry product had a material temperature of 118 °C and a water content of 23 weight %. Thereafter, the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven, thus obtaining a dried product having a water content of 7 weight %. This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 15 minutes at a wind speed of 1 m/sec and a temperature of 80 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.). A thermometer was stuck into the central portion of the resultant lumpish aggregate to measure the material temperature, which was 40 °C. In addition, the water content was 50 weight %. Next, the resultant aggregated semidry product was placed into a stainless beaker, and this vessel was airtightened by wrapping the entirety thereof with aluminum foil, and then heated at 100 °C for 1 hour.
  • a through-flow batch type drying oven 71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.
  • the semidry product After being heated, the semidry product had a material temperature of 90 °C and a water content of 45 weight %. Thereafter, the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven, thus obtaining a dried product having a water content of 7 weight %. This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 30 minutes at a wind speed of 1 m/sec and a temperature of 80 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.). A thermometer was stuck into the central portion of the resultant lumpish aggregate to measure the material temperature, which was 80 °C. In addition, the water content was 10 weight %. Next, the resultant aggregated semidry product was placed into a stainless beaker, and this vessel was airtightened by wrapping the entirety thereof with aluminum foil, and then heated at 100 °C for 1 hour.
  • a through-flow batch type drying oven 71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.
  • the semidry product After being heated, the semidry product had a material temperature of 98 °C and a water content of 9 weight %. Thereafter, the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven, thus obtaining a dried product having a water content of 6 weight %. This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 10 minutes at a wind speed of 1 m/sec and a temperature of 180 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.). A thermometer was stuck into the central portion of the resultant lumpish aggregate to measure the material temperature, which was 95 °C. In addition, the water content was 25 weight %. Next, the resultant aggregated semidry product was placed into a stainless beaker, and this vessel was airtightened by wrapping the entirety thereof with aluminum foil, and then heated at 100 °C for 1 hour.
  • a through-flow batch type drying oven 71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.
  • the semidry product After being heated, the semidry product had a material temperature of 98 °C and a water content of 23 weight %. Thereafter, the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven, thus obtaining a dried product having a water content of 7 weight %. This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 20 minutes at a wind speed of 1 m/sec and a temperature of 80 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.). A thermometer was stuck into the central portion of the resultant lumpish aggregate to measure the material temperature, which was 70 °C. In addition, the water content was 25 weight %. Next, the resultant aggregated semidry product was placed into a stainless autoclave, and then heated at 140 °C for 8 minutes. After being heated, the semidry product had a material temperature of 125 °C and a water content of 22 weight %.
  • the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven, thus obtaining a dried product having a water content of 6 weight %.
  • This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 40 minutes at a wind speed of 1 m/sec and a temperature of 170 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.), thus obtaining a dried product having a water content of 6 weight %.
  • This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • a dried product having a water content of 6 weight % was obtained in the same way as of Comparative Example 5 except that the particulate hydrogel was changed to the particulate hydrogel resultant from Production Example 2. This product was pulverized, and then classified. Measurement was made about the properties of the resultant powder of 500 ⁇ 300 ⁇ m.
  • a dried product having a water content of 6 weight % was obtained in the same way as of Comparative Example 5 except that the particulate hydrogel was changed to the particulate hydrogel resultant from Production Example 3. This product was pulverized, and then classified. Measurement was made about the properties of the resultant powder of 500 ⁇ 300 ⁇ m.
  • a dried product having a water content of 7 weight % was obtained in the same way as of Comparative Example 5 except that the particulate hydrogel was changed to the particulate hydrogel resultant from Production Example 4. This product was pulverized, and then classified. Measurement was made about the properties of the resultant powder of 500 ⁇ 300 ⁇ m.
  • a dried product having a water content of 6 weight % was obtained in the same way as of Comparative Example 5 except that the particulate hydrogel was changed to the particulate hydrogel resultant from Production Example 5. This product was pulverized, and then classified. Measurement was made about the properties of the resultant powder of 500 ⁇ 300 ⁇ m.
  • a dried product having a water content of 6 weight % was obtained in the same way as of Comparative Example 5 except that the particulate hydrogel was changed to the particulate hydrogel resultant from Production Example 6. This product was pulverized, and then classified. Measurement was made about the properties of the resultant powder of 500 ⁇ 300 ⁇ m.
  • a dried product having a water content of 6 weight % was obtained in the same way as of Comparative Example 5 except that the particulate hydrogel was changed to the particulate hydrogel resultant from Production Example 7. This product was pulverized, and then classified. Measurement was made about the properties of the resultant powder of 500 ⁇ 300 ⁇ m.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 15 minutes at a wind speed of 1 m/sec and a temperature of 80 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.). A thermometer was stuck into the central portion of the resultant lumpish aggregate to measure the material temperature, which was 40 °C. In addition, the water content was 50 weight %. Next, the resultant aggregated semidry product was treated with a microwave oven at 500 w for 3 minutes. After being heated, the semidry product had a material temperature of 95 °C and a water content of 27 weight %.
  • the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven, thus obtaining a dried product having a water content of 6 weight %.
  • This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was statically dried for 20 minutes at a wind speed of 1 m/sec and a temperature of 80 °C with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.). A thermometer was stuck into the central portion of the resultant lumpish aggregate to measure the material temperature, which was 70 °C. In addition, the water content was 25 weight %. Next, the resultant aggregated semidry product was treated with a microwave oven at 500 w for 3 minutes. After being heated, the semidry product had a material temperature of 98 °C and a water content of 15 weight %.
  • the lumpish aggregate was spread onto a wire gauze again, and then finish-dried at 150 °C for 30 minutes with the through-flow batch type drying oven, thus obtaining a dried product having a water content of 6 weight %.
  • This product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • the drying process was carried out in the same way as of Comparative Example 13 except that the aggregated semidry product was treated with a microwave oven at 1,500 w for 9 minutes.
  • the resultant dried product was pulverized, and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • the material temperature was 98 °C, and the water content was 5 weight %.
  • the dried product resultant from the finish-drying step had a water content of 4 weight %.
  • the semidry product as got out of the microwave oven had a partially scorched surface and gave out a foul smell.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was dried until the water content reduced to 20 weight % by causing a hot wind, comprising a mixed gas of water vapor and air and having a temperature of 120 °C and a dew point of 80 °C, to blow the hydrogel at a wind speed of 1 m/sec with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.).
  • a hot wind comprising a mixed gas of water vapor and air and having a temperature of 120 °C and a dew point of 80 °C
  • the hydrogel was further dried until the water content reduced to 6 weight % with an unhumidified hot wind having a temperature of 180 °C, a dew point of 5 °C, and a wind speed of 1.0 m/sec, and then the dried hydrogel was pulverized and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m.
  • An amount of 1 kg of the particulate hydrogel as obtained in Production Example 1 was dried by causing a hot wind, comprising a mixed gas of water vapor and air and having a temperature of 130 °C and a dew point of 80 °C, to blow the hydrogel for 15 minutes at a wind speed of 1 m/sec with a through-flow batch type drying oven (71-S6, made by Satake Kagaku Kikai Kogyo Co., Ltd.).
  • a hot wind comprising a mixed gas of water vapor and air and having a temperature of 130 °C and a dew point of 80 °C
  • the hydrogel was further dried until the water content reduced to 6 weight % by causing an unhumidified hot wind, having a temperature of 160 °C, a dew point of 5 °C, and a wind speed of 1.0 m/sec, to blow the hydrogel for 50 minutes, and then the dried hydrogel was pulverized and then classified. Measurement was made about the absorption capacity under no load, the extractable content, and the residual monomer content of the resultant powder of 500 ⁇ 300 ⁇ m. Absorption capacity under no load (g/g) Extractable content (%) Residual monomer content (ppm) Water-absorbent resin used Absorption capacity change ratio under no load (%) Extractable content change ratio (%) Prod.
  • an unhumidified hot wind having a temperature of 160 °C, a dew point of 5 °C, and a wind speed of 1.0 m/sec
  • the dried product. resultant from Example 6, was pulverized with a roll mill and then classified to obtain particles which passed through a sieve of 850 ⁇ m and remained on a sieve of 150 ⁇ m.
  • a surface-treated water-absorbent resin was obtained in the same way as of Example 9 except that the dried product was changed to the dried product resultant from Comparative Example 10.
  • This water-absorbent resin had an absorption capacity of 50 (g/g) under no load and an absorption capacity of 30 (g/g) under the load.
  • Example 9 As is evident from the results of Example 9 and Comparative Example 17, the water-absorbent resin is dried without being deteriorated in the present invention, therefore the resultant dried water-absorbent resin exhibits excellent absorbency under the load.
  • the water-absorbent resin is dried without being deteriorated in the present invention, therefore the resultant dried water-absorbent resin exhibits high swelling pressure.
  • the water-absorbent resin is dried without being deteriorated in the present invention, therefore the resultant dried water-absorbent resin exhibits high swelling pressure.

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Claims (5)

  1. Verfahren zur Herstellung eines hydrophilen Polymers, das die Stufen der Bildung eines Hydrogelpolymers durch Polymerisation eines hydrophilen Monomers in wässriger Lösung und des anschließenden Trocknens des Hydrogelpolymers umfasst;
    wobei das Herstellungsverfahren dadurch gekennzeichnet ist, dass die Trocknungsstufe die Stufen:
    partielles Trocknen des Hydrogelpolymers unter normalem Druck bei einer Materialtemperatur von nicht höher als 90 °C, bis der Wassergehalt des Hydrogelpolymers auf 15 ~ 40 Gew.-% verringert ist; und dann
    Wärmealterung des Hydrogelpolymers durch Halten des Hydrogelpolymers in einem Zustand, in dem die Änderung des Wassergehalts des Hydrogelpolymers innerhalb von 5 Gew.-% liegt und die Materialtemperatur im Bereich von 70 ~ 120 °C liegt, während nicht kürzer als 10 min; und dann
    Endtrocknen des Hydrogelpolymers, bis der Wassergehalt des Hydrogelpolymers im Bereich von 0-10 Gew.-% liegt, umfasst.
  2. Verfahren zur Herstellung eines hydrophilen Polymers, das die Stufen der Bildung eines Hydrogelpolymers durch Polymerisation eines hydrophilen Monomers in wässriger Lösung und des anschließenden Trocknens des Hydrogelpolymers umfasst;
    wobei das Herstellungsverfahren dadurch gekennzeichnet ist, dass die Trocknungsstufe die Stufen:
    partielles Trocknen des Hydrogelpolymers unter normalem Druck bei einer Materialtemperatur von nicht höher als 90 °C, bis der Wassergehalt des Hydrogelpolymers auf 15 ~ 40 Gew.-% verringert ist; und dann
    Wärmealterung des Hydrogelpolymers durch Halten des Hydrogelpolymers in einem Zustand, in dem der Wassergehalt des Hydrogelpolymers im Bereich von 15 - 40 Gew.-% liegt und die Materialtemperatur im Bereich von 70 ~ 120 °C liegt, während nicht kürzer als 10 min; und dann
    Endtrocknen des Hydrogelpolymers, bis der Wassergehalt des Hydrogelpolymers auf einen gewünschten Wert verringert ist.
  3. Herstellungsverfahren nach Anspruch 1 oder 2, wobei der Wassergehalt des Hydrogelpolymers, das durch die Polymerisation erhalten wurde, im Bereich von 80 ~ 60 Gew.-% liegt.
  4. Herstellungsverfahren nach Anspruch 1 oder 2, wobei die Polymerisation des hydrophilen Monomers in wässriger Lösung die Verwendung eines Persulfatsalzes umfasst.
  5. Herstellungsverfahren nach Anspruch 1 oder 2, wobei das Hydrogelpolymer, das durch die Polymerisation erhalten wurde, einen Restmonomergehalt von nicht niedriger als 10.000 ppm aufweist.
EP99122561A 1998-11-18 1999-11-12 Verfahren zur Herstellung eines hydrophilen Polymer Expired - Lifetime EP1002806B1 (de)

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US11969707B2 (en) 2018-11-13 2024-04-30 Lg Chem, Ltd. Method for preparing super absorbent polymer

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